Agonists of guanylate cyclase and their uses

1. A method of colonic cleansing, comprising administering to a subject in need thereof a unit dose of 0.01 mg to 60 mg of an effective amount of a guanylate cyclase receptor agonist (GCRA) peptide consisting essentially of the sequence of SEQ ID NO: 1.

2. The method of claim 1 , wherein said peptide is bicyclic consisting essentially of the sequence of SEQ ID NO: 1.

3. The method of claim 1 , further comprising administering to said subject an effective amount of an osmotic colonic evacuant.

4. The method of claim 2 , wherein said osmotic colonic evacuant is magnesium citrate.

5. The method of claim 2 , wherein said osmotic colonic evacuant is a phosphate salt laxative.

6. The method of claim 1 , further comprising administering to said subject an effective amount of L-glucose, lubiprostone (Amitiza), prucalopride, an agent for treating chronic constipation, or any combination thereof.

7. The method of claim 6 , wherein said effective amount of L-glucose is a unit dose of 20g-200g.

8. The method of claim 1 , further comprising administering to said subject an effective amount of a cGMP-specific phosphodiesterase inhibitor.

9. The method of claim 8 , wherein said cGMP-specific phosphodiesterase inhibitor is selected from the group consisting of sulindac sulfone, zaprinast, motapizone, vardenafil, and sildenafil.

10. A method of colonic cleansing, comprising administering to a subject in need thereof a formulation comprising a mixture of:

a. a composition comprising an inert carrier coated with GCRA peptides consisting essentially of the sequence of SEP ID NO: 1, wherein said composition comprises an enteric coating that releases the peptides at pH 5.0; and

b. a composition comprising an inert carrier coated with GCRA peptides consisting essentially of the sequence of SEQ ID NO: 1, wherein said composition comprises and enteric coating that releases the peptides at pH 6.0or pH 7.0.